Save reader state on idle

app/src/main/java/org/koitharu/kotatsu/utils/IdlingDetector.kt

@@ -0,0 +1,37 @@
+package org.koitharu.kotatsu.utils
+
+import android.os.Handler
+import android.os.Looper
+import androidx.lifecycle.DefaultLifecycleObserver
+import androidx.lifecycle.LifecycleOwner
+
+class IdlingDetector(
+	private val timeoutMs: Long,
+	private val callback: Callback,
+) : DefaultLifecycleObserver {
+
+	private val handler = Handler(Looper.getMainLooper())
+	private val idleRunnable = Runnable {
+		callback.onIdle()
+	}
+
+	fun bindToLifecycle(owner: LifecycleOwner) {
+		owner.lifecycle.addObserver(this)
+	}
+
+	fun onUserInteraction() {
+		handler.removeCallbacks(idleRunnable)
+		handler.postDelayed(idleRunnable, timeoutMs)
+	}
+
+	override fun onDestroy(owner: LifecycleOwner) {
+		super.onDestroy(owner)
+		owner.lifecycle.removeObserver(this)
+		handler.removeCallbacks(idleRunnable)
+	}
+
+	fun interface Callback {
+
+		fun onIdle()
+	}
+}